The idea that privacy can be violated like this solely because random Facebook users are interested in it and on the off-chance that family he hadn't interacted with in years might find some abstract comfort despite not being close at all is just incredibly bizarre.
At minimum, he was using a nickname.
You might think it's likely that he was keeping private his non-trail identity, but that is not the minimum explanation.
(FWIW, knowing about through-hiker culture, I don't think it's even the likely explanation, but that's just my opinion.)
I suspect those that didn't want to be on social media at all would have declined to be in the GoPro video for a longer discussion (as I likely would have, but I wouldn't have stopped a passing hiker doing a GoPro recording since that's more in the realm of a dashcam kind of thing). Fellow hikers tend to be respectful about such things.